Grid type resistor



Oct. 12, 1965 E. WEYENBERG 3,212,045

GRID TYPE RESISTOR Filed Dec. 24, 1962 2 Sheets-Shea?l 1 /y Za /3 ,WIJ

rNvENToR L/oNEL E. Wem/BERG Oct. 12, 1965 E. WEYEN BERG GRID TYPE RESISTOR Filed DSG. 24, 1962 2 Sheets-Sheet 2 L/oNEL E. WEYENBERG United States Patent O 3,212,045 GRID TYPE RESISTOR Lionel E. Weyenberg, 3845 N. 169th St., Brookfield, Wis. Filed Dec. 24, 1962, Ser. No. 246,800 Claims. (Cl. 338-316) This invention relates to an electrical resistance apparatus and more particularly to a grid type resistor employing a plurality of pre-formed grid strips which provide controlled grid movement and eliminate buckling between the grids under overload conditions.

In a grid type resistor, a series of cast or sheet metal grid strips are arranged in generally parallel relation with the ends of adjacent strips being connected together in series. Under operating conditions, the grid strips tend to expand, and under overload current conditions the strips may buckle with the result that adjacent strips may contact each other and short out the resistance. In other applications, such as railway equipment and excavators, where severe vibration occurs, the closely spaced grid strips may accidentally contact each other due to the vibration and similarly short out the resistance.

The present invention is directed to an improved grid type resistor which is fabricated from a plurality of identical pre-formed grid strips. The grid strips are arranged in generally parallel alignment and the ends of adjacent strips are connected together in series. According to the invention, each grid strip is bowed or bent in a similar direction so that under overload conditions the expansion of each grid strip will be in the same direction, with the result that the grid strips will not buckle and come in contact with one another.

More specifically, each grid strip is provided with an offset bend at one end of the strip and is also provided with a central generally V-shaped bend. The oiiset bend permits the ends of adjacent strips to be secured directly together and spaces the central portion of the adjacent strips. The central bend provides the V-shape or bowed configuration which enables all of the strips to expand in the same direction and thereby eliminates buckling.

The grid strips are of simple construction and can be cut and formed in a single operation. As the ends of adjacent strips were welded together, the use of conductive spacers between strips is eliminated. Moreover, the welding procedure is simpliiied in that the diliicult process of welding grid strips to spacer bars is eliminated with the present invention.

The grid design of the invention allows intermediate terminals or taps to be conveniently placed at Various points throughout the resistor to provide maximum flexibility in series-parallel connections. The resistor units are generally provided with current capacities up to 1000 amperes and resistance value to 25 ohms, and greater current and resistant values can be readily obtained by connecting several units together.

Other objects and advantages will appear in the course of the following description.

The drawings illustrate the best mode presently contemplated by the inventor for carrying out the invention.

In the drawings:

FIG. 1 is a plan View of the grid type resistor of the invention with parts broken away in section;

FIG. 2 is a perspective view of a grid strip;

FIG. 3 is an enlarged fragmentary sectional view showing the attachment of an end of a grid strip to a connecting rod;

FIG. 4 is a plan View of a modilied form of the invention with parts broken away in section;

FIG. 5 is an end view of the resistor shown in FIG. 4;

FIG. 6 is a section taken along line 6-6 of FIG. 4;

FIG. 7 is a plan View of a second modiiied form of the invention;

FIG. 8 is an enlarged fragmentary section taken along line 8-8 of FIG. 7, and

FIG. 9 is an enlarged fragmentary sectional view showing the attachment of a terminal strip to the grid strip.

The drawings illustrate a grid type resistor including a pair of channel-shaped end frames 1 which are connected together by rods 2. The outer ends of the rods 2 are threaded and extend through suitable openings in the frame 1, and the outer end of each rod receives a nut 3. A nut 4 is also located on each rod 2 adjacent on of the end frames 1. The nuts 3 and 4 position the end frames 1 with respect to the rods 2 and prevent relative movement between the members.

A series of generally parallel grid strips 5 are secured to the rods 2 and the ends of adjacent strips 5 are connected together in series to provide the electrical resistance. As best shown in FIG. 3, an insulating sleeve 6 is disposed on each of the rods 2, and the rod and sleeve extend through an opening 7 in the end of grid strip 5. The rod 2 and sleeve 6 also extend through an opening in a terminal 8 which is secured in conductive relation with the end grid strip in series. The terminal 8 and grid strip 5 are positioned on sleeve 6 by an insulating spacer 9 and a nut 10 which is threaded on rod 2 and bears against the spacer 9 and the end of sleeve 6. In addition, an insulating gasket 11 and a washer 12 bear against strip 5, and a spacer sleeve 13 bears against the outer surface of the washer 12 and spaces the washer 12 from a second washer 14 associated with the next grid strip 5 in the series. As shown in FIG. 3, an insulating gasket 15 and a washer 16 are located on the opposite side of the next grid strip 5 in the series to position the strip on the rods 2 and a second spacer sleeve 17 bears against the washer 16. This arrangement is repeated throughout the length of the rods 2 so that the ends of the adjacent grid strips which are secured together are iixed in spaced relation on the rods 2.

A terminal 18 is connected in electrical conductive relation with the last grid strip 5 in the series. While the drawing only shows two terminals, 8 and 18, it is contemplated that any number of terminals or taps can be employed throughout the length of the resistor.

As best shown in FIG. 1, the grid strips 5 are arranged in generally parallel relation and all of the strips are bowed or bent in the same direction. -Each grid strip includes end sections19 and 20 which are located in substantially parallel planes. The end section 19 of one grid strip is welded iiatwise to the end section 20 of the next adjacent grid strip, as shown in FIG. 1.

In order to offset or space the central portion of each grid strip from the central portion of adjacent grid strips, each strip is provided with a bent portion 21 which extends outwardly at an acute angle to the end section 19. In addition, each grid strip includes a pair of central sec- 'tions 22 and 23 which are disposed at an angle to each other to provide a generally V-shape for the central portion of the grid strip. The section 22 extends at an obtuse angle with respect to the bent portion 21, and the central sections 22 and 23 of each grid strip are disposed generally parallel with the central sections 23 and 22 of the 'next adjacent strip. As the grid strips 5 are all bent or bowedin the` same direction, any expansion of the grid Y strips under operating conditions will be in the same direction with the result that buckling of the strips will be eliminated and there will be no contact between adjacent strips under overload conditions or vibr-ations.

FIGS. 4-6 show a modified form of the invention which includes a pair of insulating support members 24 which support two rows of grid strips 25. The grid strips 25 are substantially identical to the grid strips 5 of the irst embodiment.

Each support member 24 includes a central section 26 and a pair of end sections 27 and 2S which are attached to the central section by means of brackets 29. A series of bolts 30 extend through suitable openings in the brackets 29 and support member sections, and connect the sections 26, 27 and 28 together as a unit. Each bracket 29 is provided with a mounting foot 31.

The ends of adjacent grid strips 25 are welded or otherwise connected together and are located within slots 32 formed in the edge of the central section 26. The ends of the strips 25 extend through the slots 32 Iand the end sections 27 and 28 which border the slots prevent lateral displacement of the grid strips 2S from the slots. Each grid strip 25 is provided with a hole 33 in the projecting end.

To prevent longitudinal movement of the grid strips 25 from the slots 32, a lug 34 is secured to the p-rojecting ends of a number of the grid strips in the series. As best shown in FIG. 5, the lugs 34 have a larger size than the -slots 32 and project laterally beyond the central section 26. The lugs prevent the ends of the grid strips 25 from slipping out of the slots 32. As shown in the drawings, a pair of the lugs 34 are associated with the grid strips 25 at each end of the resistor and it is contemplated that any number of lugs may be employed for this purpose.

The grid strips 25 are substantially identical to the grid strips 5 and include end portions 35 and 36, which are located in sub-stantially parallel planes, and a bent section 37, which is disposed at an acute angle to the end section 35. In addition, each strip includes a pair of central sections 38 and 39 which are disposed at an angle to each other to provide the generally V-shape for the grid strip.

As shown in FIG. 4, one-half of the series of V-shaped strips 25 face in one direction and the other half faces in the opposite direction. This results in the center of the resistor being open and provides la cool center are-a which further resists buckling and enables the resistor to carry a heavier load.

In this embodiment, the ends of the grid strips 25 project outwardly through Iche support members 24 and vfunction as terminals so that no auxiliary terminals or taps are required. The projecting ends of the grid strips 25 thereby serve as an unlimited number of terminals so that the capacity of the resistor can be readily varied as desu-ed. As in the case of the iirst embodiment, the central section of each grid strip is disposed generally parallel to the central section of the adjacent strips and due to the V or bowed shape, the strips will tend to expand in the same direction which eliminates buckling and contact between the strips.

To assemble the resistor shown in FIG. 4, the ends of the grid strips are initially welded together and the lugs 33 are then secured by welding to a number of the projecting ends of the grid strips. The ends of the strips 25 are then inserted within the slots 32 in the central section 26 and the end `sections 27 and 23 are then joined to the central section by means of the brackets 29 and bolts 30.

The resistor shown in FIG. 4 is a low cost, high capacity resistor which eliminates the use of spacers, washers, gaskets and other elements which are normally employed to space and connect the ends of the grid strips together. Greater current and 4resistance values are available by connecting several resistors units together to provide any arrangement of series, parallel or series-parallel connections.

While the above description is directed to grid strips vhaving generally V-shaped configuration, it i-s contemplated that the grid strip may be curved or otherwise bent at various locations to provide the bowed or bent configuration which will enable the strips to expand in the same direction to thereby eliminate buckling.

FIGS. 7-9 show a modified form of the invention comprising a frame 40 which supports two rows of studs 41. As best shown in FIG. 8, each stud 41 is secured within an opening in frame 40 by nuts 42 and 43 which are located on opposite sides of the `trarne and are threaded on the stud.

A continuous -grid strip 44 is bent around each stud 4) and is electrically insulated from each stud by an insulating sleeve 45 and a pair of insulating washers 46 and 47. The upper end of each stud receives a washer 4S and a nut 49.

As shown in tFIG. 7, the grid strip 44 is continuous and extends from one row of studs to the other and back with the portions of the strip extending between the rows of studs having a generally V shape and being substantially parallel.

The ends of the grid strip 44 are bent around the respective studs, as shown in FIG. 9, and welded to the portion of the grid strip approaching the stud. In addition, a terminal strip 50 is welded to the overlapping portions of the grid strip and extends outwardly from the row of studs. Additional terminal strips 5t) can be secured to the grid strip at various locations throughout its length, if desired.

As the portions of the grid strip extending between the rows of studs are all lbent or bowed in the same direction any expansion of these portions will be in the same direction so that there will be no contact between adjant portions under overload conditions or vibration.

Various modes of carrying out the invention are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention.

I claim:

1. In an electrical resistance device, a supporting structure, a series of generally parallel grid strips carried by the supporting structure with the ends of adjacent strips being connected together in series, each strip having end portions located in generally parallel planes and having a iirst section extending from one end portion and defining an obtuse angle therebetween, each strip having a second section extending at an angle from said rst section and each strip also including a third section connecting said second section with the opposite end portion, said third section extending at an angle to said opposite end portion and in a reverse direction with respect to the second section, said second and third sections forming a generally V-shaped coniiguration for the strip to thereby permit each strip to expand in the same direction when said strips are subjected to operating current conditions and prevent buckling of the strips under overload conditions.

2. In an electrical resistance device, a supporting structure, and a series of sheet metal grid strips carried by the supporting structure with the ends of adjacent strips being connected together in series, said strip being disposed in generally parallel relation and each strip having a substantially greater width than thickness, the central portion of each strip being bent in a direction parallel to its width to provide the central portion of each strip with a generally V shape, and each strip having a bend located at one end of said strip to offset the central section of said strip from the end portions, said V shape permitting each strip to expand in the same direction when the strips are subjected to operating current conditions and preventing buckling of the strips under overload conditions.

3. In an electrical resistance device, a pair of insulated support members with each support member including a central section having a series of spaced slots in a side edge thereof and said support member including an end mem- :ber disposed in abutting relation to said side edge to thereby close off said slots, a series of grid strips with ends of adjacent grid strips being connected together to form a series-connected resistor, the connected ends of said strips projecting through said slots in the respective central sections of said support members, and means connected to the portion of said connected ends projecting through said slots for preventing displacement of said connected ends from said slots.

4. In an electrical resistance device, a pair of support members fabricated of insulating material, each support member including a central section having a series of slots disposed in a side edge and said support member including an end section disposed in abutting relation to said side edge to close olf said slots, a series of sheet metal grid strips carried by the supporting members with the ends of adjacent grid strips connected together to form a seriesconnected resistor, the connected ends of said strips projecting through the slots in said central section of the respective support members, said strips being disposed in generally parallel arrangement with the central portion of each strip :being `bent in a direction parallel to its width to provide the central portion of each strip with a generally V shape, a lug connected to at least one of said connected ends associated with each support member and disposed on the outer surface of said support member to prevent said grid strips from slipping through said slots, and means for removably securing said end section to the central section to prevent lateral displacement of the connected ends from said slots.

5. In an electrical resistance device, a pair of supporting members, a series of identical sheet metal grid strips carried by the supporting structure with each end of each grid strip connected directly to an end of an adjacent grid strip to provide a series connection between said grid strips, the connected ends of said grid strips mounted on the supporting members with each pair of connected ends on one supporting member disposed in a plane between parallel planes extending through adjacent pairs of connected ends on the other supporting member, said strips being disposed in generally parallel arrangement with the central portion of each strip being bent in a direction parallel to its width to provide the central portion of each strip with a generally V shape and each grip strip being provided with a second bend located between the first bend and a pair of connected ends to maintain the generally parallel spacing between the grid strips throughout their length.

References Cited by the Examiner UNITED STATES PATENTS 2,721,920 10/55 Weide `338-318 X 2,812,410 y11/57 Du Bois 338-316 X 2,858,402 10/58 Griffes et al. 338-58 2,928,062 3/60 Du Bois 338-316 2,969,516 1/61 Du Bois 338-284 FOREGN PATENTS l113,836 9/41 Australia. 661,996 111/51 Great Britain.

RICHARD M. WOOD, Primary Examiner. 

1. IN AN ELECTRICAL RESISTANCE DEVICE, A SUPPORTING STRUCTURE, A SERIES OF GENERALLY PARALLEL GRID STRIPS CARRIED BY THE SUPPORTING STRUCTURE WITH THE ENDS OF ADJACENT STRIPS BEING CONNECTED TOEGTHER IN SERIES, EACH STRIP HAVING END PORTIONS LOCATED IN GENERALLY PARALLEL PLANES AND HAVING A FIRST SECTION EXTENDING FROM ONE END PORTION AND DEFINING AN OBTUSE ANGLE THEREBETWEEN, EACH STRIP HAVING A SECOND SECTION EXTENDING AT ANGLE FROM SAID FIRST SECTION AND EACH STRIP ALSO INCLUDING A THIRD SECTION CONNECTING SAID SECOND SECTION WITH THE OPPOSITE END PORTION SAID THIRD SECTION EXTENDING AT AN ANGLE TO SAID OPPOSITE END PORTION AND IN A REVERSE DIRECTION WITH RESPECT TO THE SECOND SECTION, SAID SECOND AND THRID SECTION FORMING A GENERALLY V-SHAPED CONFIGURATION FOR THE STRIP TO THEREBY PERMIT EACH STRIP TO EXPAND IN THE SAME DIRECTION WHEN SAID STRIPS ARE SUBJECTED TO OPERATING CURRENT CONDITIONS AND PREVENT BUCKLING OF THE STRIPS UNDER OVERLOAD CONDITIONS. 